Iron base high temperature alloy



United States Patent 2,744,821 I RON BASE HIGH TEMPERATURE ALLOY Lee E. Osman, Marblehead, Mass., assignor to General Electric Company, a corporation of New York No Drawing. Application December 13, 1951, Serial No. 261,576

6 Claims. (Cl. 75-124) The present invention relates to an iron base high temperature alloy. More particularly, it is concerned with and has as its principal object the provision of a wrought In my prior patents, 2,442,209 and 2,492,761, there. are

disclosed high temperature alloys having precipitation hardenable characteristics as a result of the presence therein of significant and effective quantities of beryllium. While these alloys possess satisfactory tensile and rupture properties, both at room and elevated temperatures, their use has been restricted due to the questionable status of beryllium as a health hazard.

In accordance with the present invention there has been provided a beryllium-free alloy possessing all of the desirable characteristics of the beryllium-containing alloys. The alloy of the present invention contains from 0.03 to .4 percent by weight carbon, 0.4 to 1 percent silicon, 1 to 2 percent manganese, 16 to 19 percent chromium, 12 to 36 percent nickel, 0.8 to 1.2 percent tungsten, 1.75 to 2.25 percent molybdenum, 0.5 to 1.25 percent aluminum, 2 to 2.5 percent titanium with the balance iron, except for incidental impurities and not over 1.5 percent of various addition elements which do not materially aflectthe characteristics of the base alloy. One such addition element is up to 1.5 percent colurnbium. In certain cases this alloying element is believed to be a desirable component of the alloy, although, because of its high cost and unavailability at the present time, it is not considered an essential component of the alloy of the present invention- Preferred alloys within the present invention exhibiting the maximum tensile and stress rupture characteristics are those in which the carbon content is from 0.1 to 0.3 percent, the chromium content from 17 to 19 percent and the nickel content from to 3.6 percent. Columbium is not present in the preferred alloys.

The alloys of the present invention may be readily .forged at temperatures from 1 600 to 2200 F. with the preferred forging temperatures being in the neighbor-hood of 2000 F. In order to develop the optimum properties of the alloys, they are subjected to a solution treatment at from 950 to 1250 C., preferably from 950 to 1050 C., followed by water quenching and an aging treatment at a temperature of from 650 to 750 C., preferably about 725 C. The alloys will ordinarily be held at the solution temperatures for from 1 to 3 hours and at the aging or precipitation hardening temperatures for from about 10 to 24 hours. The resultant alloys possess a Rockwell-C hardness from about to 35.

In Table I there are set forth the compositions, in weight percent, of a number of alloys within the scope of the preset invention along with the compositions of a number of alloys containing aluminum and titanium in amounts greater than or less than the ranges hereinbefore specified.

.The room temperature and high temperature properties of all of the alloys of Table I are tabulated in Table II.

Table I Alloy G, Si, Mn, Cr, Ni, W, Mo, Ob, Al, T1, N0 perperperperperperperperperpercent cent cent cent cent cent cent cent cent cent M-133 .24 5 1.6 16. 6 13 1. 0 2. 2 1.08 0. 7 2. 3 M2l6.- 31 8 1. 17. 2 24. 1 84 2.10 1.05 0.7 2. 3 M134. 26' 6 1. 6 18.1 23. 5 2.0 1. 27 0. 7 2. 3 M-215 .16 87 1. 72 17.8 35.8 1.00 2.00 1. 47 O. 7. 2.3 11 LC'.. .09 .76 1.29 17.1 25.8 .91 2.13 1.07 0.7 2.0 12LC .08 .89 .71 15.9 35.4 .91 2.1 1.2 0.7 2.11 13110.. .15 .44 1.82 18.6 24.1 .90 2.2 1.2 2.3 13 H0. .35 .84 1.42 17.4 23.9 .67 2.6 1.2 1.9 14 LO .03 .47 1.54 18.3 36.2 .79 2.1 2.38 14 H0. .27 .54 1.47 18.8 36.6 1.07 2.2 .75 2.4 M150 .34 .49 1. 34 17.4 23. 7 .72 2.00 1. 43 2.00 M217. 3 72 1. 51 18. 2 23. 7 68 2.10 99 2. 5 51 M208 .35 81 1.77 16. 6 23. 0 75 2.10 1. 12 2. 0 1.0 M210 .30 77 1.86 18. 3 23. 2 1. 12 2. 00 1.22 1. 5 1. 5

Table 11 1,200 F. Stress Room Temperature Tensile Prop. Rupture Properties Alloy O 7 1 000 Heat Ofiset Tensile Red. of

Treat- Yield Strength, gggi' Area, E33;

ment 1 Strength, p. s. 1. Per- S S p. s. i. cent M433 A 60, 720 143, 220 22 28. 2 52, 800 41, 000 M2l6 B 100 158, 330 23 31. 8 60, 000 44, 000 Ml34.. B 75, 350 157, 930 22 29. 4 61, 000 48, 000 M215 B 105, 260 177, 600 17. 7 22. 2 66, 000 58, 000 11 LC 13 85, 500 160, 700 12. 5 13. 8 56, 000 47,000 12 LC. B 95, 580 174, 620 14 '14. 9 60, 000 49, 000 13 LC.. B 85, 830 162, 500 20. 5 34 54, 000 13 HC. 13 77, 750 154, 250 22. 3 37. 8 64, 000 50,000 14 LC B 102, 200 174, 500 19. 5 27. 6 54, 000 14 HO. B 81, 000 154, 800 22. 5 38. 2 58, 500 51', 500 M-150 C 43, 121, 800 27 7 35. 5 49, 000 r M217. B 61, 540 133, 970 25. 5, 30. 5 000 t M208 B 49, 950 123, 530 33. 3 I 49. 7 50, 500 43, 500 M210 B 64, 920 130, 230 26 38. 1 54, 000 45, 000

1 Optimum Heat treatments of forged material: A-1 hr. at 1,200 0., water quench; 15 hrs. at 6509 0., air cool. B-1 hr. 9501,050 0., water quench; 15 hrs. at 725 0., air cool. C-l hr. 1,250 C., water quench; 15 hrs. at 725 0., air cool.

.Rockwell-C scale was obtained. On the other hand, yalloy M134 could be hardened to a maximum. of about 35.5 Rc. Further, the alloys containing the lower contents of nickel, such as the M- 133 alloy, require a higher solu-v tion temperature in the neighborhood of about 1200 C. and a lower age hardening temperature of around 600 or 650 C. to obtain optimum precipitation hardness. The higher. nickel alloys can be. solution treated at temperatures in. the neighborhood of 1000 C. and have an optimum aging temperature-up. to about 725 0. Thus, the high nickel alloys have better heat stability than the low nickel alloys. They are also superior in this respect to the beryllium-containing alloys referred to hereinbefore, all of which tend to over-age at temperatures of about 725 C. Likewise, the higher nickel alloys possess a greater yield, tensile and rupture strengths than the low nickel alloys.

Micro-structure studies of the alloyshave indicated that the low nickel alloys consist of a mixture of alpha and gamma solid solutions together with precipitated compounds and carbides, while the high nickel alloys are completely austenitic with the matrix consisting entirely of a gamma-solid solution and containing precipitated compounds and carbides.

.test results obtained on alloys M150, M217, M208 and M-210. Alloy M150 contains only aluminum" and no titanium while the remaining alloys contain more than the prescribed amount of aluminum and less than the prescribed amount of titanium. From a comparison of the strength and rupture properties of these alloys with the properties of the remaining alloys whose compositions and properties are given in Tables I and II, it will be seen that best results are obtained when the aluminum content is from 0.5 to 1.25 percent and the titanium content from 2 to 2.5 percent by weight; The alloys containing these quantities of aluminum and titanium can be readily melted with few inclusions providing the melting procedure is carefully controlled, and the cast product can be readily forged.

The effect of increased nickel content and the properties of the alloys will be noted from a comparison of alloys M133, M216, M-134 and M--215. While the aluminum and titanium contents are more efiective and more critical than the nickel content of the alloys, the 36 percent nickel alloy (M215) has excellent strength and well-balanced properties, especially for an iron base alloy. The 24 percent nickel alloys M216 and M134 have very good strength although not quite the same as the higher nickel alloy. In general, all of the alloys containing at least 20 percent nickel have good all-around properties for gas turbine or supercharger wheel material and for any high temperature application up to about 1350 F. Alloy M-216 which has a nickel content of about 24 percent has an austenitic structure and differs from the duplex structure of both alpha and gamma solid solutions in the 13 percent nickel alloy M-133. The higher nickel content alloys require higher aging temperatures to develop maximum strength, thus indicating their greater high temperature stability. Likewise, lower solution temperatures are needed to obtain the best age hardening characteristics. This is just the reverse from the treatments required for the comparable beryllium-containing alloys described hereinbefore, or for most ofl'ier precipitation-hardening iron base alloys.

In general, the alloys of the present invention can be successfully aged anywhere from 500 C. to 750 C. with practically no eifect on their rupture strength. Solution temperatures in the 950 to 1050 C. range appear to produce better rupture strengths than do solution temperatures above this range as, for example, at 1150 C.

The best high temperature properties such as rupture and creep strength are obtained in those alloys containing the higher carbon contents of at least 0.15 percent and preferably in the neighborhood of 0.25 to 0.35 percent carbon. For example, the alloys possessing the greatest lOOO-hour stress rupture values at 1200 F. were alloys 'M215, 14 HO, and 13 HC, respectively containing 0.16,

0.27, and 0.35 percent carbon.

While most of the alloys described in Tables I and II contain columbium in amounts up to about 1.5 percent, this element is not essential as shown by the properties of alloys 13 LC, 13 EC, 14 LC and 14 HC in which this element has been omitted. Alloy 13 HO, for example, had a 1200" F. stress rupture at hours of 64,000 p. s. i. which compares favorably with the same values for the columbium-containing alloys having the prescribed amounts of aluminum and titanium and is much superior to stress rupture values of the last four alloys set forth in Table I, all of which contain aluminum and titanium in amounts outside the prescribed range.

For best results the alloys of the present invention should be prepared under carefully controlled conditions. It is desirable that the aluminum and titanium additions be made at the end of the heat, after the heat has been deoxidized by the silicon and manganese additions. The aluminum is first added to the heat followed by the titanium addition just before pouring. Only sufiicient time between the addition of the titanium, either as ferroor nickel-titanium, and the pouring of the heat is allowed for the titanium to go into solution and difiuse uniformly through the melt. The important factor here is the amount of uncombined titanium, i. e., the titanium in solid solution or in an intermetallic compound, which is present in the heat. Titanium combined, for example, as an oxide, carbide, or nitride will not impart precipitation hardening effect and, therefore, will contribute little or nothing to the strength of the alloy.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A heat-treatable iron base alloy containing, by Weight, about 0.03 to 0.4 percent carbon, 04 to 1 percent silicon, 1 to 2 percent manganese, 16 to 19 percent chromium, 12 to 36 percent nickel, .8 to 1.2 percent tungsten, 1.75 to 2.25 percent molybdenum, 0.5 to 1.25 percent aluminum, 2 to 2.5 percent titanium; balance iron and incidental impurities which do not materially affect the physi cal properties of said alloy.

2. A heat-treatable iron base alloy of claim 1 in which the carbon content is from 0.1 to 0.3 percent, the chromium content from 17 to 19 percent, and the nickel content from 20 to 36 percent.

3. The alloy of claim 2 containing up to about 1.5 percent columbium.

4. A wrought precipitation hardened alloy consisting essentially, by weight, of 0.03 to 0.4 percent carbon, 0.4 to 1 percent silicon, 1 to 2 percent manganese, 16 to 19 percent chromium, 12 to 36 percent nickel, .8 to 1.2 percent tungsten, 1.75 to 2.25 percent molybdenum, 0.5 to 1.25 percent aluminum, 2 to 2.5 percent titanium, balance iron with not more than 1.5 percent of the additional elements and incidental impurities which do not materially affect the physical properties of said alloy.

5. The alloy of claim 4 in which the carbon content is at least 0.15 percent and the nickel content is at least 20 percent.

6. The alloy of claim 4 containing up to 1.5 percent columbium.

References Cited in the file of fliis patent UNITED STATES PATENTS 2,048,167 Pilling et al. July 21, 1936 2,519,406 Scott et a1 Aug. 22, 1950 2,523,838 Malcolm Sept. 26, 1950 

1. A HEAT-TREATABLE IRON BASE ALLOY CONTAINING, BY WEIGHT, ABOUT 0.03 TO 0.4 PERCENT CARBON, 0.4 TO 1 PERCENT SILICON, 1 TO 2 PERCENT MANGANESE, 16 TO 19 PERCENT CHROMIUM, 12 TO 36 PERCENT NICKEL, .8 TO 1.2 PERCENT TUNGSEN, 1.75 TO 2.25 PERCENT MOLYBDENUM, 0.5 TO 1.25 PERCENT ALUMINUM, 2 TO 2.5 PERCENT TITANIUM; BALANCE IRON AND INCIDENTAL IMPURITIES WHICH DO NOT MATERIALLY AFFECT THE PHYSICAL PROPERTIES OF SAID ALLOY. 